In recent years, there has been developed, for the purpose of protecting, insulatively enclosing or repairing a joint portion of electric wire, cable, pipe, etc., a method of employing a self-shrinkable elastic tube which is capable of covering the joint portion without necessitating the application of heat in place of the conventional method of using a heat-shrinkable tube. This self-shrinkable elastic tube is made of a rubber-like elastic material and is normally supported in advance on a tubular rigid supporting body whereby the inner diameter of the elastic tube is kept in an expanded state.
In the employment of the self-shrinkable elastic tube, the self-shrinkable elastic tube is inserted over a joint portion of power cable for instance while it is kept in an expanded state as mentioned above, and then the supporting body is withdrawn from the self-shrinkable elastic tube, thereby allowing the self-shrinkable elastic tube to be shrunk diametrally, thus obtaining the joint portion which is hermetically covered by the elastic tube.
There has been conventionally proposed the following method as a means to expand the diameter of such an elastic tube.
Namely, first of all, an elongated bag-like expandable hollow body twice as long as that of the self-shrinkable elastic tube is prepared. Then, the fore half portion of this expandable hollow body is inserted into the self-shrinkable elastic tube, and then the expandable hollow body is entirely expanded by means of a pressurized air whereby diametrally expanding the self-shrinkable elastic tube. Thereafter, a supporting body disposed on the side of the rear half portion of the expandable hollow body is forcibly introduced into the fore half portion of the expandable hollow body where the self-shrinkable elastic tube is disposed. Then, the pressurized air in the expandable hollow body is withdrawn thereby allowing the expandable hollow body to shrink. As a result, a self-shrinkable elastic tube rested on the supporting body with the self-shrinkable elastic tube being kept expanded can be obtained (Japanese Patent Unexamined Publication S/63-74624).
However, this conventional method is accompanied with the problem that since a bag-like expandable hollow body is rendered to be interposed between a supporting body and a self-shrinkable elastic tube in the process of resting the self-shrinkable elastic tube on the supporting body in this method, the hollow body is ultimately left strongly sandwiched between the supporting body and the self-shrinkable elastic tube. As a result, it is very difficult to remove the supporting body from the self-shrinkable elastic tube at the occasion of mounting the self-shrinkable elastic tube on the joint portion of a power cable for instance.